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1. Field of the Invention
This invention pertains generally to wire-wound ferromagnetic cores used in electromagnetic devices, and more particularly to a method and apparatus for increasing the amount of effective ferromagnetic mass without increasing device size.
2. Description of the Background Art
A variety of electromagnetic devices utilize a set of electrical windings wound upon a ferromagnetic core. The core typically comprises a set of laminated plates which are stamped-out from sheets of ferrous material, and which are configured with slots, or other means, for the proximal retention of the electrical windings.
An electrical generator typifies one such electromagnetic device, wherein a ferromagnetic stator core retains a set of windings. A typical stator is created from a set of stamped-out steel plates which are laminated together forming a stack. Each of the steel plates contains cutouts such that, when the plates are laminated together, channels are formed through which a set of windings can be routed. These windings are routed from one such channel to another within the stator. It should be understood that ferromagnetic cores may also be fabricated by processes that do not require laminating a stack of plates, for example the core may be pressed or molded from ferromagnetic materials.
For example, FIG. 1 shows a typical wire-wound stator 10, wherein a ferromagnetic core 12 has a number of slots 14 for receiving windings. FIG. 2 depicts the slots 14 with entry openings 16 shown prior to being wound. The portion of core material between each slot forms a core tooth 18. Referring again to FIG. 1, a set of windings 20 are shown routed through slots 14 between core teeth 18. A series of end turns 22 comprise portions of windings 20 which lie outside of slots 14 and bend from one slot to another slot. After exiting ferromagnetic core 12, windings 20 form a bend prior to entering another slot 14 of ferromagnetic core 12. As a result of these exterior bends, an intra-turn air space 24 is created between the turns of the wiring past the exterior faces 26 of stator core 12. Although a significant intra-turn air space typically exists for applications with medium to high current windings, the size and shape of the airs space depends on the layout of the core and how tightly the wires are bent.
The majority of stators follow this same basic design, despite the fact that the electromagnetic device industry is highly competitive. A need still exists, however, for increasing the efficiency of stator cores and wound cores in general. The present invention satisfies that need, as well as others, and overcomes the deficiencies of previously developed solutions.
The present invention is directed to increasing the amount of ferromagnetic material which may be retained proximal to the windings on a ferromagnetic core. A standard core configuration may be modified to include radiused ferromagnetic protrusions capable of nestling between the intra-turn spaces between the windings. A number of embodiments are provided which exemplify the inclusion of intra-turn ferromagnetic protrusions within an electromagnetic core.
By way of example, and not of limitation, in one embodiment of the invention an intra-turn lamination member, containing intra-turn ferromagnetic projections, is added to the ends of the ferromagnetic core. The intra-turn lamination member includes radiused protrusions of ferromagnetic material that nestle within the intra-turn spaces of the winding as the wires exit the ferromagnetic core. The intra-turn lamination member preferably comprises ferromagnetic material and is attached to the stator so as to increase the ferromagnetic mass proximal the windings. In another embodiment, the ferromagnetic core is manufactured or fabricated with integral ferromagnetic radiused protrusions which nestle in the intra-turn windings. In another embodiment the intra-turn ferromagnetic projections are added to only small portions of the electromagnetic core over which a winding is received.
An object of the invention is to increase the efficiency of a wound electromagnetic device without increasing the core size.
Another object of the invention is to reduce the probability of nicking the insulation on the wire strands which comprise the windings.
Another object of the invention is to decrease the amplitude of the air noise associated with air movement proximal to a wound core used in a moving electromagnetic device.
Another object of the invention is to provide enhanced electromagnetic core efficiency while substantially retaining the use of current manufacturing processes.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.